1. Field of the Invention
The invention pertains to the coloring, tinting, and dyeing of lenses, particularly ophthalmic lenses used in eyeglasses. Specifically, the invention relates to gradient coloring, tinting, and dyeing of lenses.
2. Description of the Prior Art
In the process of manufacturing lenses it is often desirable and necessary to add a color, dye, or tint to the lens. In many cases it is very desirable to have a subtle tonal gradation from relatively opaque at the top of the lens to a very mildly tinted or tint free condition at a selected place on the lens, usually from the middle to the bottom. The purpose of the gradient tinting process is to obstruct the passage of bright light and glare, particularly from overhead light, such as sunshine, through the lens to the eye, while permitting good vision through the maximum surface area of the lens.
In the past, optical processing laboratories have customarily performed the gradient coloring process by entirely manual means. Operator fatique and the irregularities and inconsistancies typical of manual processes were readily apparent in the quality of the final product. The mechanized processes to which the manual techniques have yielded have only slightly improved the product.
Devices currently available for gradient coloring, tinting, and dyeing of lenses, particularly those used for opthalmic applications typically produce harsh, hard, often irregular, and thus highly visible patterns on the lens being coated. These results are particularly objectionable when prescription lenses are involved. They are highly undesirable in all cases from the standpoints of adverse vision affects and appearance of the wearer. Currently used devices typically perform the process in slow, abrupt and discontinuous movements with undesirable pauses at the point of maximum immersion of the lens. The discontinuous movements, in addition to creating streaks and lines, do not provide continuous agitation of the coloring liquid to provide a uniform coloring medium on each immersion cycle.